Why Does Armpit Hair Stop Growing?

Hair grows in phases. Each hair follicle begins, continues and stops growing hair. Hair follicles repeat this progression at different rates depending on both internal regulations (like hormones) and sometimes external (like food).

However, basically the longer hair follicle, found on the scalp, has a longer growth period than pubic or armpit hair follicles. So the hair on the scalp is shed very slowly compared to the other regions. Compare this:

Scalp hair is about 1 cm per month or 0.34 to 0.36 mm per day throughout life. Meanwhile, eyelash or brow growth at 0.16 mm per day in average. Beard hair at 0.38 mm/day. Once again, it depends on hormone. I shave my beard every three days, while my friend does it every day.

What about pubic and axillary hair? They grow almost as fast as scalp hair at 15, but slow with age and have a much faster follicle turn over time. The genes control it all automatically. That’s why your armpit hair can’t reach your stomach, even if you never shaved it since you were born.

Controlling Sweat a la Celebs

There's a name for excessive sweating, hyperhidrosis, a condition that most commonly affects the armpits and the palms, as well as the head and feet. Dermatologists estimate that about 8 million Americans suffer from hyperhidrosis, while many more experience undiagnosed troublesome sweating.

While there is no definition for how much sweating is too much, anyone whose sweaty palms or damp armpits are causing physical or psychological discomfort can and should speak with a doctor about the highly effective treatment options.

But if you simply want to treat sweating once and forget about it for months, there is no more effective option than Botox (or Myobloc, the other, lesser-known botulinum toxin currently approved for use in the United States). This is the secret weapon of many celebrities, for example, who don't want to risk underarm stains on the red carpet!

By blocking the chemical that stimulates sweat glands, Botox significantly curbs sweating within days of treatment. The injections hurt for a few seconds, and the pocketbook may hurt even more: treatment can cost up to $1,000 and needs to be repeated every 4-6 months. (Insurance covers the injections under the arms in many cases but never covers the hand injections.) I have been consistently impressed, though, by how well Botox treatments work.

Did you know that your dermatologist can also prescribe you a strong antiperspirant, like Drysol, that uses high concentrations of aluminum hydroxide (up to 25% vs. the 1-2% concentration in over-the-counter antiperspirants) to temporarily clog sweat ducts? Applied at night - two or three days in a row to start, and once or twice a week thereafter - and washed off in the morning, these products can significantly curb sweating throughout the day.

Yes, sweating is an important way for the body to regulate its temperature, but limiting your ability to sweat over small surface areas is entirely safe. Moreover, many of my patients have reported significant improvement in their quality of life after seeking treatment for this common condition. (Leslie Baumann, M.D.)